In the LTE (Long Term Evolution) standard whose specification is being developed by the 3GPP, a mobile station UE performing communications by using a carrier with a carrier frequency F1 is configured to perform measurement on a measurement target frequency F2 within a measurement gap in the carrier with the carrier frequency F1, as shown in FIG. 13.
An information element “MeasGapConfig” in “MeasConfig” transmitted by a radio base station eNB is configured to designate such measurement gap.
Here, in section 8.1.2.3.1.1 of the 3GPP TS 36.133, the LTE standard requires fulfillment of a requirement, as a system performance, that “a mobile station UE must detect a cell (an inter-frequency cell, a different carrier cell) using a CC with a measurement target frequency designated by a radio base station eNB, in a measurement gap designated by the radio base station eNB within a predetermined time period TIdentify_Inter.
Similarly, in another section in the 3GPP TS 36.133, the LTE standard requires fulfillment of a requirement that the mobile station US must detect a cell (an inter-RAT cell, a different RAT cell) using a radio access technology (RAT) of a measurement target designated by a radio base station eNB.
In addition, in the LTE-Advanced standard whose specification is being developed by the 3GPP, studies on “CA (Carrier Aggregation)” are being advanced.
The mobile station UE performing CA is configured to perform communications with the radio base station eNB by using multiple “Component Carriers (CC)” with different carrier frequencies.